Abstract: AIMTo investigate the water-soluble steroidal saponins in total saponin from Dioscorea nipponica Makino and look for new active compounds. METHODSThe compounds were isolated with silica gel, PTLC and HPLC, and their structures were elucidated by acid hydrolysis, physical and chemical data and spectral analysis (IR, NMR, MS, HMQC, HMBC) as well as chemical correlations. RESULTSThe two steroidal saponins (water-insoluble saponin and water-soluble saponin) were isolated from the total saponin of Dioscorea nipponica Makino. The structures were elucidated as diosgenin 3-O-α-L-rhamnopy ranosyl (1→2)-［β-D-glucopyranosyl (1→3)］-β-D-glucopyranoside (I), diosgenin 3-O-［α-L-rhamnopyranosyl (1→3)-α-L-rhamnopyranosyl (1→4)-α-L-rhamnopyranosyl (1→4)］-β-D-glucopyranoside (II). CONCLUSIONCompound II is a new steroidal saponin and firstly isolated from Dioscorea nipponica Makino. It was named as dioscin Dc.